MSAV_snippet3.swift

// Step 1
guard let xibItems = Bundle.main.loadNibNamed("ListingView", owner: self, options: nil), let firstXibView = xibItems[0] as? UIView else {
    fatalError("Xib is empty or first view is not a UIView")
}
// Step 2
firstXibView.translatesAutoresizingMaskIntoConstraints = false

// Step 3
let viewConstraints = [NSLayoutAttribute.top, NSLayoutAttribute.left, NSLayoutAttribute.bottom, NSLayoutAttribute.right].map { (attribute) -> NSLayoutConstraint in
    return NSLayoutConstraint(item: firstXibView, attribute: attribute, relatedBy: .equal, toItem: self, attribute: attribute, multiplier: 1, constant: 0)
}

// Step 4
addSubview(firstXibView)
addConstraints(viewConstraints)